CWE-1222: Insufficient Granularity of Address Regions Protected by Register Locks

What is Insufficient Granularity of Address Regions Protected by Register Locks?

• Overview: Insufficient Granularity of Address Regions Protected by Register Locks refers to a situation where a large address region is protected by a single register lock. This can cause conflicts between the need for some addresses to remain writable during operation and the security requirement to lock system configurations after boot.

• Exploitation Methods:

• Attackers could exploit this by modifying writable parts of the address region that should be protected.
• Common techniques include manipulating the boot process to unlock regions or exploiting software that writes to these addresses.

• Security Impact:

• Direct consequences include unauthorized modification of system configurations.
• Potential cascading effects could involve system instability or opening further vulnerabilities.
• Business impact includes potential data breaches, loss of system integrity, and non-compliance with security standards.

• Prevention Guidelines:

• Ensure address regions protected by register locks are appropriately granular.
• Implement hardware designs that separate critical configurations into individually locked regions.
• Regularly review and update firmware and bootloader settings to adhere to security best practices.
• Use security tools to audit hardware and firmware configurations for vulnerabilities.

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Technical Details

Likelihood of Exploit: Not specified

Affected Languages: Not Language-Specific

Affected Technologies: System on Chip

Vulnerable Code Example

# Vulnerable code demonstrating insufficient granularity in address region protection
class MemoryManager:
    def __init__(self):
        # Large memory block with a single lock control
        self.memory_block = [0] * 1024  # A block of 1024 addresses
        self.memory_locked = False  # Single lock for the entire block

    def lock_memory(self):
        # Lock control applied to the entire block
        self.memory_locked = True

    def unlock_memory(self):
        # Unlock control applied to the entire block
        self.memory_locked = False

    def write_memory(self, address, value):
        # Vulnerability: The entire block must be unlocked to write to a single address
        if not self.memory_locked:
            self.memory_block[address] = value
        else:
            raise PermissionError("Memory is locked.")

In this vulnerable example, the entire memory block is controlled by a single lock. This means that to modify even a single address, the whole block must be unlocked, potentially exposing other addresses to unauthorized modifications.

How to fix Insufficient Granularity of Address Regions Protected by Register Locks?

To fix the vulnerability of insufficient granularity in address region protection, we need to ensure that memory protection is applied at a finer granularity. Instead of locking an entire block of memory, we should allow locking at smaller regions or even individual addresses. This approach prevents unnecessary unlocking of the entire block for modifications to a single address, maintaining security while allowing necessary operations.

Here are the steps to implement the fix:

1. Introduce a granular locking mechanism, such as a lock for each address or smaller memory segments.
2. Ensure that the lock/unlock operations only affect the specific address or segment required.
3. Maintain overall security by ensuring no unauthorized access occurs when modifying the memory.

Fixed Code Example

# Fixed code demonstrating granular address region protection
class MemoryManager:
    def __init__(self):
        # Memory block with individual locks for each address
        self.memory_block = [0] * 1024  # A block of 1024 addresses
        self.locks = [False] * 1024  # Individual lock for each address

    def lock_address(self, address):
        # Lock control applied to the specific address
        self.locks[address] = True

    def unlock_address(self, address):
        # Unlock control applied to the specific address
        self.locks[address] = False

    def write_memory(self, address, value):
        # Check the lock status for the specific address
        if not self.locks[address]:
            self.memory_block[address] = value
        else:
            raise PermissionError(f"Memory at address {address} is locked.")

In the fixed code, each address in the memory block now has its own lock. This allows specific addresses to be locked and unlocked independently, thereby providing more granular control over memory protection. This approach mitigates the risk of unauthorized modifications by requiring unlock actions to be precise and address-specific. This ensures that only the necessary parts of the memory are exposed when modifications are required.